1. Field of the Invention
The present invention relates to a magnetic sensor, particularly to a magnetic sensor for detecting a change of an external magnetic field in terms of a change in an electric current value.
2. Description of the Related Art
Conventionally, there has been known a magnetic sensor which is formed by using a chip coil as shown in FIG. 4. Such kind of a magnetic sensor comprises a ferrite core section 1 including a lower flange member 2, an upper flange member 3 and a trunk member 4, and a coil 5 wound around the trunk member 4, in a manner such that it is allowed to detect an electric current flowing through the coil 5 by detecting a change in a magnetic flux xcfx86 passing through the core section 1. For example, when a magnetic flux xcfx86 is generated by a permanent magnet attached on a rotating body, the magnetic sensor can be used to provide a function as a sensor for detecting rotation.
However, since the magnetic sensor shown in FIG. 4 has a structure formed by winding a core wire around the core section 1, there has been a problem that its productivity is low and its sensitivity is not satisfactory. Indeed, it will be favourable if the upper flange member 3 is made to have a large area, since such a flange member is used to collect the magnetic flux xcfx86. On the other hand, there is a limitation on the size of the flange member. This is because in a general manufacturing process, since the lower flange member 2 is chucked and an automatic wire winding machine is used to wind the coil 5 around the trunk, it can not be avoided that the upper flange member 3 is made to have a small size. Further, since the lower flange member 2 and the upper flange member 3 are very likely to get chipped or cracked, a special care should be taken when handling these flange members.
It is an object of the present invention to provide a laminated type magnetic sensor which is suitable to be manufactured in a large amount, has a high sensitivity, and is easy to handle.
In order to achieve the above object, a magnetic sensor of the present invention comprises: a coil section formed by laminating together a plurality of non-magnetic sheets each having a coil pattern formed thereon and having a magnetic body disposed on the center of the coil pattern; a first outer layer section and a second outer layer section, each being formed by laminating together magnetic sheets, the first and second outer layer sections are laminated on obverse and reverse surfaces of the coil section, respectively; electrodes electrically connected with end portions of the coil patterns.
Thus, the magnetic sensor of the present invention has a laminated structure including the coil section, the first outer layer section and the second outer layer section both disposed to cover up the front and back surfaces of the coil section, and is allowed to be manufactured in mass production process by using the same process for manufacturing a conventional electronic component such as a conventional laminated type inductor and a conventional capacitor. In fact, the magnetic sensor of the present invention is easy to handle. The first or second outer layer section is formed to provide a function of collecting an external magnetic flux. Since such an outer layer section is set to have the same area as that of the coil section and thus has a relatively large area, it is sure to effectively collect the external magnetic flux and allow it to penetrate through the magnetic body located in the center of each coil pattern. Accordingly, the magnetic sensor of the present invention is sure to obtain an increased sensitivity.
Further, in the magnetic sensor of the present invention, each of the sheets forming the coil section has its substantially central portion formed by a magnetic body and its surrounding portion formed by a non-magnetic body, further includes a coil pattern formed on the non-magnetic body. Therefore, the magnetic sensor has a good magnetic efficiency and its coil section can be easily handled by treating the sheets one by one.